Mon, Aug 15, 2022: 4:00 PM-4:15 PM
513E
Background/Question/MethodsGlobally, species are undergoing range shifts in response to climate change. However, fewstudies have assessed the effects of range-shifting species as they establish in new communities,despite the potential for significant impacts. In southern California, the predatory whelkMexacanthina lugubris has undergone a northward range shift of more than 100 km in the pastfour decades. Whelks are important intermediate predators in coastal marine ecosystems, and theintroduction of a novel species could alter community structure through changes to existingspecies interactions. We traced the history of the whelk’s range shift and assessed potentialimpacts on native species using an integrated approach, consisting of field surveys, as well asfeeding and thermotolerance experiments. We compared tide height distributions (presence andabsence) of native whelks at sites with and without Mexacanthina using gamma hurdle models.Feeding experiments were analyzed with a two-way interactive ANOVA to assess the effects ofpredator and prey compositions, and a logistical regression was used to calculate LT50 andquantify differences in survival by species and temperature.
Results/ConclusionsWe found Mexacanthina has continued to expand northward. At sites where Mexacanthinaoccurred, native whelk presence was affected by Mexacanthina presence (p< 0.001), tide height(p< 0.001), and their interaction (p=0.002) with native whelks occurring more often lower in theintertidal. The same pattern was true as Mexacanthina density increased (p< 0.001). Native whelkdensities also peaked lower in the intertidal due to an interactive effect of tide height andMexacanthina presence (p=0.02) and density (p=0.04). In laboratory experiments, we found thatthe presence of Mexacanthina, but not conspecifics, led to reduced growth in the native whelkAcanthinucella spirata (p< 0.001). There was no effect of prey composition or the interactionwith predator composition. Additionally, the range-shifting whelk showed similar thermaltolerance as the native Acanthinucella, but was able to tolerate higher temperatures than Nucellaemarginata (p=0.02). This suggests further impacts as a result of climate warming as manyspecies are likely to undergo range shifts as a coping mechanism for changing climaticconditions, but communities are unlikely to shift as a whole due to species-specific responses. Bystudying the impacts of range-shifting species, like Mexacanthina, we can better understand howclimate change will alter existing community structure and composition.
Results/ConclusionsWe found Mexacanthina has continued to expand northward. At sites where Mexacanthinaoccurred, native whelk presence was affected by Mexacanthina presence (p< 0.001), tide height(p< 0.001), and their interaction (p=0.002) with native whelks occurring more often lower in theintertidal. The same pattern was true as Mexacanthina density increased (p< 0.001). Native whelkdensities also peaked lower in the intertidal due to an interactive effect of tide height andMexacanthina presence (p=0.02) and density (p=0.04). In laboratory experiments, we found thatthe presence of Mexacanthina, but not conspecifics, led to reduced growth in the native whelkAcanthinucella spirata (p< 0.001). There was no effect of prey composition or the interactionwith predator composition. Additionally, the range-shifting whelk showed similar thermaltolerance as the native Acanthinucella, but was able to tolerate higher temperatures than Nucellaemarginata (p=0.02). This suggests further impacts as a result of climate warming as manyspecies are likely to undergo range shifts as a coping mechanism for changing climaticconditions, but communities are unlikely to shift as a whole due to species-specific responses. Bystudying the impacts of range-shifting species, like Mexacanthina, we can better understand howclimate change will alter existing community structure and composition.